MICRONAS unveils complete solution for Dolby Digital TV surround sound (9910)

Digital and multi-channel: Cinema sound at home

Freiburg, August 29, 1999 - On the occasion of IFA '99, the chip manufacturer MICRONAS presents a surround sound solution for high-end TV sets and AV receivers based on the digital audio standard Dolby Digital. It is set to bring to the living room the surround sound system that has already established itself in the cinema.

Dolby Digital (Digital Audio Compression Standard AC-3) is a digital system for multi-channel coding of audio signals. With Dolby Digital, five audio channels (left, center, right, surround left, and surround right) plus an effect channel (LFE, i.e. low-frequency effects) can be transmitted simultaneously. As the LFE channel requires only one-tenth of the transmission rate of the audio channels, the system is also known as "5.1-channel".

In contrast to the known analog surround sound system Dolby Surround Pro Logic, which creates more of a diffuse spatial impression, Dolby Digital permits the precise spatial reproduction of the sound sources. This is achieved through five equivalent audio channels - including two surround channels - which feature the full frequency range from 20 to 20,000 Hz and high channel separation of over 90 dB.In addition, using an LFE loudspeaker, the extremely low frequency range from 20 to 120 Hz (structure-borne sound), which is perceptible rather than audible, can be reproduced with greater intensity.

By comparison, Pro Logic offers only one, bandwidth-limited (100...7000 z) surround channel which does not permit the right/left separation of the surround signal radiated from the rear. Furthermore, due to the nature of the system, the channel separation between the front and rear speakers is generally of the order of only 30...40 dB. These compromises were adopted in order to be able to use the conventional analog transmission paths for Pro Logic.

Unlike Pro Logic, Dolby Digital is a purely digital system. Today, the main Dolby Digital sound sources are DVD (Digital Versatile Disk) and digital television broadcasting via cable or satellite. Digital television programs with Dolby Digital multi-channel sound will be available in Germany as from IFA '99 via the TV provider Pro 7.

Three chips for five-point-one channels

MICRONAS offers a chipset comprising three signal processors for decoding Dolby Digital:

• The Dolby Digital Decoder MAS 3528 decompresses and processes the AC-3 data stream (e.g. from a DVD player). It features a direct S/PDIF input, so a separate S/PDIF receiver IC is not required. The decoded data (5 + 1 channels for Dolby Digital plus 2 channels for Pro Logic or Stereo Remix) are output via an eight-channel I2S output. The two stereo or Pro Logic outputs are needed for playback via headphones or for VCR recording via the SCART interface.
• The Multi-Standard Audio Processor MSP 4450 handles the complete audio processing in the TV set from the second IF stage onwards. It is a refined version of the successful MICRONAS IC already installed in more than 50 million sets worldwide. The MSP 4450 works with a sampling rate of 48 kHz, corresponding to a maximum signal bandwidth of 24 kHz which is unique in the world of TV. The IC incorporates nine integrated D-A converters and an expanded, eight-channel I2S interface.
• The eight-channel Surround Sound Processor DPL 4519 possesses three additional stereo converter pairs so that the chipset features a total of fifteen D-A converters for the simultaneous operation of six speakers, stereo headphones and SCART interface. Operated as a coprocessor for the MSP 4450, the DPL 4519 also provides the computing power required for the initial sampling of 32/44.1 kHz signal sources to 48 kHz.

The ICs are supplied in the package types PLCC44 and QFP44 (MAS 3528) or PQFP80 (MSP 4450, DPL 4519). Samples of all three ICs, now close to full-scale production, will be available from September 1999. High-volume production is to commence in the fourth quarter of 1999. Along with the ICs, MICRONAS provides customers with a reference design of the Dolby Digital application described above, already geared to production requirements, as well as a PC-supported demonstration software package; the effort and expense required on the part of the customer in terms of matching the software are minimal.

In the pipeline: Virtual Dolby Digital

In the near future, MICRONAS will offer the chipset with an additional Virtualizer circuit which enables Dolby Digital surround sound to be reproduced through only two speakers. The Virtualizer technology developed by MICRONAS (and already available for the Pro Logic system) has been certificated by Dolby Laboratories. Thanks to the authentic signal quality, Virtual Dolby Digital is superior to its analog counterpart Virtual Dolby Pro Logic.